GALENA: tabular DCG parsing for natural languages

[Abstract] We present a definite clause based parsing environment for natural languages, whose operational model is the dynamic interpretation of logical push-down automata. We attempt to briefly explain our design decisions in terms of a set of properties that practical natural language processing systems should incorporate. The aim is to show both the advantages and the drawbacks of our approach.España. Gobierno; HF96-36Xunta de Galcia; XUGA10505B96Xunta de Galcia; XUGA20402B9

COVID-19 severity and mortality in patients with CLL: an update of the international ERIC and Campus CLL study

Patients with chronic lymphocytic leukemia (CLL) may be more susceptible to Coronavirus disease 2019 (COVID-19) due to age, disease, and treatment-related immunosuppression. We aimed to assess risk factors of outcome and elucidate the impact of CLL-directed treatments on the course of COVID-19. We conducted a retrospective, international study, collectively including 941 patients with CLL and confirmed COVID-19. Data from the beginning of the pandemic until March 16, 2021, were collected from 91 centers. The risk factors of case fatality rate (CFR), disease severity, and overall survival (OS) were investigated. OS analysis was restricted to patients with severe COVID-19 (definition: hospitalization with need of oxygen or admission into an intensive care unit). CFR in patients with severe COVID-19 was 38.4%. OS was inferior for patients in all treatment categories compared to untreated (p < 0.001). Untreated patients had a lower risk of death (HR = 0.54, 95% CI:0.41–0.72). The risk of death was higher for older patients and those suffering from cardiac failure (HR = 1.03, 95% CI:1.02–1.04; HR = 1.79, 95% CI:1.04–3.07, respectively). Age, CLL-directed treatment, and cardiac failure were significant risk factors of OS. Untreated patients had a better chance of survival than those on treatment or recently treated

The evolving landscape of COVID‐19 and post‐COVID condition in patients with chronic lymphocytic leukemia: A study by ERIC, the European research initiative on CLL

In this retrospective international multicenter study, we describe the clinical characteristics and outcomes of patients with chronic lymphocytic leukemia (CLL) and related disorders (small lymphocytic lymphoma and high-count monoclonal B lymphocytosis) infected by SARS-CoV-2, including the development of post-COVID condition. Data from 1540 patients with CLL infected by SARS-CoV-2 from January 2020 to May 2022 were included in the analysis and assigned to four phases based on cases disposition and SARS-CoV-2 variants emergence. Post-COVID condition was defined according to the WHO criteria. Patients infected during the most recent phases of the pandemic, though carrying a higher comorbidity burden, were less often hospitalized, rarely needed intensive care unit admission, or died compared to patients infected during the initial phases. The 4-month overall survival (OS) improved through the phases, from 68% to 83%, p = .0015. Age, comorbidity, CLL-directed treatment, but not vaccination status, emerged as risk factors for mortality. Among survivors, 6.65% patients had a reinfection, usually milder than the initial one, and 16.5% developed post-COVID condition. The latter was characterized by fatigue, dyspnea, lasting cough, and impaired concentration. Infection severity was the only risk factor for developing post-COVID. The median time to resolution of the post-COVID condition was 4.7 months. OS in patients with CLL improved during the different phases of the pandemic, likely due to the improvement of prophylactic and therapeutic measures against SARS-CoV-2 as well as the emergence of milder variants. However, mortality remained relevant and a significant number of patients developed post-COVID conditions, warranting further investigations

An Operational Model for Parsing Definite Clause Grammars with Infinite Terms

. Logic programs share with context-free grammars a strong reliance on well-formedness conditions. Their proof procedures can be viewed as a generalization of context-free parsing. In particular, definite clause grammars can be interpreted as an extension of the classic contextfree formalism where the notion of finite set of non-terminal symbols is generalized to a possibly infinite domain of directed graphs. In this case, standard polynomial parsing methods may no longer be applicable as they can lead to gross inefficiency or even non-termination for the algorithms. We present a proposal to avoid these drawbacks, focusing on two aspects: avoiding limitations on the parsing process, and extending the unification to composed terms without overload for non-cyclic structures. 1 Introduction Grammar formalisms based on the encoding of grammatical information in unification-based strategies enjoy some currency both in linguistics and natural language processing. Such formalisms, as is the ..

M. Vilares Ferro

The objective of this paper is to study a practical approach to deal with nontermination in definite clause grammars. We focus on two problems, loop and cyclic structure detection and representation, maintaining a tight balance between practical efficiency and operational completeness. In order to guarantee the validity of our conclusions, we first map our study to a common situated framework, where the effectiveness of each approach will be examined and, later, compared by running experiments.

An Operational Model for Parsing Fixed-Mode DCGs

Logic programs share with context-free grammars a strong reliance on well-formedness conditions. Their proof procedures can be viewed as a generalization of context-free parsing. In particular, definite clause grammars can be interpreted as an extension of the classic context-free formalism where the notion of finite set of non-terminal symbols is generalized to a possibly infinite domain of directed graphs. In this case, standard polynomial parsing methods may no longer be applicable as they can lead to gross inefficiency or even non-termination for the algorithms. We briefly present a proposal to avoid these drawbacks. We choose to work in the context of fixed-mode programs, focusing on two aspects: Avoiding limitations on the parsing process, and extending the unification to composed terms without overload for non-cyclic structures. Key Words: DCG, Dynamic Programming, Logical Push-Down Automaton, Cyclic Term. 1 A parsing strategy for DCGs Strategies for executing definite clause ..

Tabular Algorithms for TAG Parsing

We describe several tabular algorithms for Tree Adjoining Grammax paxsing, creating a continuum from simple pure bottom-up algorithms to complex predictive algorithms and showing what transformations must be applied to each one in order to obtain the next one in the continuum

Construction of Efficient Generalized LR Parsers

We show how LR parsers for the analysis of arbitrary context-free grammars can be derived from classical Earley&apos;s parsing algorithm. The result is a Generalized LR parsing algorithm working at complexity O(n 3 ) in the worst case, which is achieved by the use of dynamic programming to represent the non-deterministic evolution of the stack instead of graph-structured stack representations, as has often been the case in previous approaches. The algorithm behave better in practical cases, achieving linear complexity on LR grammars. Experimental results show the performance of our proposal. Keywords: LR automata, non deterministic context-free parsing, dynamic programming, natural language processing. 1 Introduction LR parsing, one of the strongest and most efficient class of parsing strategies for context-free grammars (CFGs), is a two fold process: first, the grammar is compiled into a finite-state machine called LR automaton, which has two associated tables of actions and goto&apos;s [1]..